Create SECURITY.md

Author: vsch

SECURITY.md

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+# Security Policy
+
+## Supported Versions
+
+The following versions are supported. The current version is 0.64.x and is actively developed and maintained.
+Version 0.42.x is still widely used and vulnerabilities can be addressed
+in this version if they are critical.
+
+| Version | Supported          |
+| ------- | ------------------ |
+| 0.64.x  | :white_check_mark: |
+| 0.50.x  | :x:                |
+| 0.42.x  | :white_check_mark: |
+| < 0.42.x | :x:               |
+
+## Reporting a Vulnerability
+
+Please report vulnerabilities by opening an issue. You can additionally report vulnerabilities
+by e-mail on the GitHub account.
+
+I will do my best to address vulnerabilities as soon as possible with a new patch release.